Convoluted Cockney rhyming slang for 'a-se'; Arris, an abbreviation of Aristotle, rhyming with bottle, and thereafter leading to bottle and glass rhyming with 'a-se'.
I think it comes from the French word, 'aras' (sp?), meaning something like 'behind'.
Shakespeare's plays very often feature an 'arras' - a curtain at the back that people hide behind or retreat behind when they want a little privacy. 'Polonius behind the arras' is a famous tragicomic scene in Hamlet, where the unfortunate Polonius, hiding behind the arras, is mistaken for someone else and stabbed.
Thanks to all for answering. I do remember reading Bill Bryson's version of the truth in "Mother Tongue" and it was the version shaneystar has given. Although I had read this, I thought it would be wise to ask others for their take on the derivation of "arris." After all, the more that one reads the web, wikipedia, etc., the less certain one becomes as to what is the truth, or likely the truth!